Microsoft's Windows Vista has yet to win over many businesses nearly a year after it was first made available to enterprises.

Many OEMs continue to offer 'downgrade' programmes to provide users with earlier versions of Windows.

Vista was launched to great fanfare in January 2007. By April, however, users began to pine for Windows XP, prompting some companies to offer entire lines of PCs with XP pre-installed rather than Vista.

Microsoft's Windows Life-Cycle Policy lists 31 January 2008 as the last day that OEMs will be allowed directly to license Windows XP. The licence for system builders will expire 12 months later.

The company does not give any deadline for downgraded copies of the operating system, however, noting that licences could be given after the end of the operating system's availability deadline.

Among those offering the downgrade is Lenovo, which has a special section on its web site dedicated to Vista downgrades. The company plans to offer the downgrade option until 31 July 2008.

However, analysts have suggested that that the problem may not be entirely down to Windows Vista and that, after five years on the market, a battle-tested Windows XP may be filling the needs of many enterprise users.

"XP is a much better product than people think it is," Rob Enderle, principal analyst at the Ender le Group, told vnunet.com.

"People are not screaming to get off of XP, and Vista is not providing a compelling reason to do so."

Michael Cherry, lead operating systems analyst at Directions on Microsoft, told vnunet.com that performance may also be an issue, and that some customers may simply decide that a quick XP machine is better than a sluggish Vista machine.

"For whatever reason OEMs decided not to soup-up the machines, he said. " Despite having a long beta cycle, I'm still not seeing a lot of machines that are really well designed for Vista."